body {
    background-color: rgb(218, 208, 208);
}
.big {
    width: 500px;
    height: 1000px;
    margin: auto;
    overflow: hidden;
    background: rgb(89, 51, 150);
}
ul {
    margin-top: 10px;
    margin-right: 40px;
}
li {
    margin-top: 5px;
    border-bottom: 1px solid #000;
}
.commonbtn {
    background: rgb(127, 127, 160);
    width: 100px;
    margin-bottom: 8px;
    cursor: pointer;
}
#content {
    width: 350px;
    height: 60px;
    margin-left: 10px;
}
.sodiff {
    width: 500px;
    margin: auto;
}